1. Technical Field of the Invention
The present invention relates in general to a device that prevents excessive discharge of a rechargeable battery. More specifically, the present invention relates to a device that prevents excessive discharge of the battery by disconnecting loads connected to it and shuts itself off to completely prevent further discharge.
2. Description of the Related Art
With the advancement of technology in electric power generating industry, battery systems have become increasingly important in providing back-up energy in emergency situations. It is essential in emergencies and during a power failure that the battery systems perform as designed. The battery backup system supplies required power to the loads until the battery voltage drops to a certain level. When the battery voltage reaches the certain level, the inverter flashes light indicators or alerts by any alerting means. If the power failure persists for an extended period of time, it may lead to the issue of dead batteries.
There are many systems to protect the backup batteries from excessive drainage. One such system effectively prevents excessive discharge of a rechargeable battery that is either detachable from or internal to an electrical apparatus. The circuit has a battery voltage detector, a comparator to compare the battery voltage with a reference voltage, and a controller to cut-off power drain from a discharged battery when its voltage drops below the reference voltage. In addition, the discharged battery is electrically cut-off from both the load and the comparator.
Another system utilizes a device in conjunction with a battery which is connected to an electrical load. The device includes a microprocessor having a cut off voltage level which is set so that when the battery reaches the cut off voltage, sufficient energy remains in the battery engine ignition. The microprocessor generates an output signal whenever the battery voltage is less than or equal to the cut off voltage level and further the device generates a battery disconnect signal which disconnects the battery from the electrical load. Even though the electrical loads are disconnected, the device keeps drawing power from the battery as the device is still working. If the situation continues, the battery is drained to a point of no return. At the point of no return, the batteries cannot be recharged and has to be replaced at a very high cost.
In order to address the need for monitoring and controlling the battery power consumption, battery low-voltage protectors have been proposed that discloses a set of electrical switches and a control process. Irrespective of whether the voltage drop of the battery is quick or slow, after a pre-defined period of time, the system checks whether the battery voltage is below a pre-determined level. If the battery voltage is below the pre-determined level, the system will cut off the electrical connection between the battery and the load. However, when the battery is cut off from the load, the electrical switches are still connected with the battery, which means that the battery is still in an electricity discharging state.
In the course of developing battery rundown protection systems, a system responsive to the voltage of a battery to disconnect the battery from the electrical loads prior to the point at which the battery becomes too discharged. The apparatus which operates to disconnect the battery from the loads is inhibited and is maintained for a timed period sufficiently long in duration to prevent excessive discharge. While such systems have been adequate for the purpose, the system installation is complex.
Further, a switching device is connected in series with the rechargeable battery and that switching device is turned off to cut off battery discharge when battery voltage drops below a predetermined value. The switching device is maintained in the off state until the battery reaches a voltage slightly higher than the predetermined value. The system then turns the switching device on when the battery reaches a voltage slightly higher than the predetermined value. The system utilizes a hysteresis characteristic between the discharge cut off voltage and the discharge restart voltage. The use of hysteresis between the discharge cut off and restart voltages prevents switching device chattering during self recovery of the battery voltage after discharge cut off. Moreover, setting the hysteresis width between the discharge cut off voltage and the restart voltage to prevent chattering is difficult.
Hence, it can be seen, that there is a need for a device that is simple to install for protecting the batteries from excessive discharge. Further, the needed device would shut down all the loads connected to the battery and shuts itself off to completely prevent excessive battery discharge. Moreover, the needed device would reconnect the loads to the battery on retrieving the AC input for recharging the batteries.